A method of this kind is described in German Patent No. DE 101 48 217.5, in which an injector whose valve needle is joined to a piezoactuator is provided for the injection of fuel. When a voltage is applied to the piezoactuator, it experiences a change in length that it transfers to the valve needle. The latter therefore lifts off from its valve seat so that fuel under high pressure can be injected from the injector into the combustion chamber of the internal combustion engine.
In order to activate the piezoactuator, provision is made for generation, by a precontrol operation, of a setpoint which not only is dependent on the desired mass or quantity of fuel to be injected, but in which further influencing variables that might result in a distortion of the setpoint are also taken into account. Such influencing variables are, for example, the temperature of the injector or aging thereof, or the like.